1. Field of the Invention
This invention relates generally to systems for collecting and preserving tissue samples, and more particularly, to a system that enables small pieces of human tissue or stool samples to be rapidly immersed and preserved at room temperature in toxic preservatives, for later molecular and structural analysis, without danger for the user of exposure to the toxic preservatives.
2. Description of the Prior Art
Preservation of human tissues and stool samples for molecular and structural analysis frequently requires rapid immersion of samples in highly toxic preservatives, some of which produce volatile fumes that are dangerous to breathe, according to accompanying material data safety sheets. There is a need for a system that allows introduction of the sample into a storage container or sample chamber that is sealed off from the preservative, and that enables rapid movement of the preservative into the sample chamber after the chamber has been sealed.
Several devices exist for collecting fluid samples and preserving their RNA and DNA by immediate treatment with toxic volatile preservatives. These known devices include, for example:                (a) Paxgene™ Blood RNA System—This is a PreAnalytix/BD Vacutainer™ product for preserving RNA in blood. The device is operated like an ordinary Vacutainer™ blood sample collection arrangement except that the tube contains a proprietary preservative called PAXgene. In this arrangement, blood is collected during venipuncture and is sucked into the tube, without exposure of the user to its contents, upon the piercing of the Vacutainer™ plug with the phlebotomy needle. PAXgene™ tubes are an approved medical device for the purpose of collecting and preserving blood RNA. However, the utility of this known arrangement is limited to the collection of fluid samples, and is not useful in the collection of solid samples, such as stool samples.        (b) Oragene™DNA Self-Collection Kit—DNA from Saliva from DNA Genotek                    In this known arrangement, a volatile toxic chemical preservative is contained under an internal disk. A saliva sample is inserted on top of the disk. When the top of the device is screwed all the way down, the disk is rotated, allowing access of the preservative to the saliva with which it mixes. The known Oragene DNA Self-Collection Kit constitutes a way to collect and preserve large amounts of DNA from saliva. One feature of this known arrangement is that saliva samples do not require special handling or storage because the DNA in Oragene is stable for years at room temperature. However, the utility of this known arrangement is limited to the collection of fluid samples, and is not useful in the collection of solid samples, such as stool samples.                        (c) Oragene devices: Disk device and Tube device: The disk in this known arrangement prevents a stool or tissue sample from becoming fully immersed in the preservative fluid. Both disk and tube device: The total volume of the preservative is less than 2 ml. This is too small of a volume of preservative for the amounts of stool or tissue typically collected, which need to be preserved in at least 5 ml of preservative each. There is no mechanism that assures that if the sample is tissue or stool (rather than liquid, which the device was designed for) that it would stay fully immersed in the preservative since the preservative can run back into the source chamber of the preservative, leaving the tissue/stool sample behind.        
Even if the Oragene tube device is modified to accommodate a larger volume, such as 7.5 ml, the system falls short of achieving the desired goals. More specifically, with larger volumes, the fluid fills the lower chamber (which is only 5 mL in volume) so high that fluid leakage out the threads occurs as the top section is being screwed in. Nevertheless, a volume of 7.5 ml would be necessary to assure complete immersion of the sample regardless of the orientation of the device.
This problem is exacerbated by the fact that there is no “pressure relief” mechanism, so that as the upper part is screwed in, the pressure inside the device increases as the top is screwed in further to make the final cutting of the inner membrane and seal. In fact, when fully closed, the Oragene tube device has a larger positive pressure that might promote leakage of the contents if damaged or inadequately sealed.
There is a need, therefore, for a system for collecting solid tissue samples, such as stool samples, that can accommodate a relatively large volume of preservative fluid.
There is additionally a need for a system for collecting solid tissue samples, such as stool samples, that can accommodate a relatively large volume of preservative fluid and that does not leak, particularly when the system is pressurized.
There is a further need for a system for collecting individual solid tissue bio-samples.
There is a still further need for a system for collecting individual solid tissue bio-samples that can easily be used by relatively unskilled individuals for effecting self collection.